Many aircraft gas turbine engines are supplied with lubricant from a pump driven lubrication supply system. In particular, the lubrication supply pump, which may be part of a pump assembly having a plurality of supply pumps on a common, engine-driven or electric motor driven shaft, draws lubricant from a lubricant reservoir, and increases the pressure of the lubricant. The lubricant is then delivered, via an appropriate piping circuit, to the engine. The lubricant is directed, via appropriate flow circuits within the engine, to the various components that may need lubrication, and is collected in one or more recovery sumps in the engine. One or more of the pump assembly pumps then draws the lubricant that collects in the recovery sumps and returns the lubricant back to the reservoir.
Gas turbine engines, including propulsion engines, auxiliary power units, and various other turbomachines, may need to be started up over a broad range of ambient conditions. Designing a gas turbine engine system, including its associated lubrication supply system, to start following prolonged cold-soaked conditions can be a challenge. During such a start, the system needs to supply adequate engine torque-speed-fuel-fire, as well as adequate lubricant flow to at least the more critical lubricant-wetted components of the engine. Typically, lubrication supply systems are optimally designed for at hot, steady state at maximum altitude, which leaves more than the needed performance during a cold-start. As a result, during a cold-start, as well as certain other system startup conditions, more power is consumed by the lubrication supply systems than may be needed to fully implement the system startup.
Hence, there is a need for a system and method of controlling power consumed by a lubrication supply system during lubricant system startup. The present invention addresses at least this need.